Amélioration de la fiabilité des évaluations environnementales des bâtiments

The work of this thesis focused on the improvement of the reliability of environmental assessments of buildings by a better control of the origin and amplitude of uncertainties. This thesis has permitted:-The development of a methodology for evaluating the uncertainties in the LCA of building;-The construction and enrichment of a database capitalizing uncertainties in material and product scale used in support of the assessment of building's uncertainties;-Development of a contribution and sensitivity analysis, which allowed the identification of key parameters influencing on the LCA results and in the robustness of study;-The development of a methodology for robust comparisons of projects based on contribution analysis and sensitivity analysis.-Identification of optimal environmental dimensions of reinforcing concrete structures. This study also identified the evolution of environmental impacts on function of building's dimensions. The methodologies used are suitable to developers of LCA software to enhance the functionality of using comparisons of projects (this work can be implemented in the ELODIE software).The results can be used by architects, civil engineers, thermal engineers, statisticians, environment and life cycle Engineers, enabling the identification of the most impacting contributors and those influencing most the outcome's uncertaintiesLe travail de la thèse a consisté en l'élaboration d'une méthodologie pour permettre des comparaisons robustes des modèles ACV bâtiments. Cette thèse a permis :-Le développement d'une méthodologie d'évaluation des incertitudes dans l'ACV du bâtiment ;-La construction et l'enrichissement d'une base de données capitalisant les incertitudes à l'échelle matériau et produit et utilisable en support à l'évaluation des bâtiments ;-Le développement d'une méthodologie d'analyse de contribution et de sensibilité, qui a été mise en application au travers de la modélisation de 16 projets de maisons individuelles et 16 projets d'immeubles collectifs, ce qui a permis d'identifier les paramètres clés qui influencent les plus les résultats de l'évaluation ainsi que la robustesse de l'étude.-Le développement d'une méthodologie permettant des comparaisons robustes des projets basée sur la méthodologie d'analyse de contribution et de sensibilité.-L'identification des optimums environnementaux des dimensions des structures porteuses des immeubles collectifs. Cette étude a permis également d'identifier l'évolution des impacts environnementaux en fonction des paramètres de dimensionnement des structures. Pour les dimensions optimales, les comparaisons – basées sur la méthodologie de comparaison précédemment développée – des impacts environnementaux de deux structures en béton armé ont été effectuées.Les méthodologies mises en place sont utilisables :-Elles peuvent être utiles aux développeurs de logiciels d'ACV pour améliorer les fonctionnalités d'aide aux comparaisons des projets (au CSTB ce travail sera implémenté dans le logiciel ELODIE).Les résultats obtenus sont utilisables :-Par les architectes, ingénieurs du génie civil, thermiciens, statisticiens, ingénieurs de l'ACV, en leur permettant d'identifier les contributeurs les plus impactant et ceux dont l'influence sur les résultats est la plus incertaine

Environmental Benefits when Reusing Load-Bearing Components in Office Buildings: A Case Study.

This case study applies life-cycle assessment methods to the preliminary design of an office building in order to quantify the benefits achieved when reusing its load-bearing components. Results show that the production of the load-bearing system would account for 40% of the global warming potential indicator. The slabs are responsible for 65% of the environmental impacts among all structural elements and should be considered for reuse first. Compared to traditional constructions built from first-use material, a fictitious reuse of undamaged load-bearing components over three consecutive use cycles would reduce the global warming potential indicator by 25%. The global warming potential of reuse is eventually computed according to three repartition methods, highlighting the need to separate the life-cycle footprints related to production, use, and end-of-life more systematically

Benefits of wooden structure reuse:the case of an Austrian building

The building sector is responsible for 39% of greenhouse gas (GHG) emissions; thus, it has a significant amount of potential to reduce the effects of climate change. Several active- and passive solutions and strategies have been developed and proposed in the literature. Among them, wood is highlighted as a promising solution to minimize GHG from buildings. However, the benefits, especially in the circular economy, are not fully evaluated due to methodological choices. Motivated by this knowledge gap, this article aims to evaluate the benefits of wood reuse compared to traditional building construction solutions. For this purpose, we have calculated the environmental impacts of a building situated in Graz, Austria. Four different scenarios are considered. The first scenario is a fully reinforced concrete building. The second scenario is a structural beam-column made from reinforced concrete with walls made of concrete blocks. The third scenario is a beam-column made from reinforced concrete with external walls based on clay blocks. Finally, the last scenario is a full wooden building. Following the standardized life cycle assessment (LCA) method, global warming potential (GWP) is calculated through a 0/0 approach. These evaluations were made possible by correlating the impacts released from producing wooden elements and the uptake of biogenic carbon from the forest. Without considering the possibility of material reuse, the wooden structure has a 5 % lower GWP value than the reinforced concrete building. Comparatively, the other building scenarios have almost similar impacts as the building in reinforced concrete. In the case of material reuse, the wooden structure building shows potential to develop projects with 44% lower environmental impacts

Structural Design with Reclaimed Materials: an Elastic Gridshell out of Skis

This paper presents the design and construction of a 36m2 gridshell, the rigidity of which is achieved through the bending of an initially flat grid of 210 reclaimed skis. The generated waste for its production is near zero as it is mostly built from discarded material. Its construction process is such that it can be disassembled and reassembled multiple times without scaffolding and by means of traditional tools only. After a brief introduction on the need for reducing embodied carbon and waste in structures through reuse, the paper sets up the constraints that have driven the definition of the pavilion, the main one being the extension of the lifetime of high-performance sport equipment by reclaiming their intrinsic mechanical properties. The paper then details the encountered unusual aspects in the design process and how they have been overcome – i.e. sporadic material supply, categorization of mechanical properties, physical alteration of these properties, and uncertainties in the numerical modelling of both the structural analysis and the construction process. Eventually, we conclude that reclaimed skis as a material have the potential to be as good as conventional timber when designing elastic gridshells. A series of future directions for this emerging field of research are also laid out

Introduction of a dynamic interpretation of building LCA results: the case of the smart living (lab) building in Fribourg, Switzerland

Although a building lifetime is not predictable, it is an essential data in the yearly impact calculation. Yet, in the assessment of the environmental impacts of building the lifetime is considered as a fixed value. The purpose of this study is to introduce a new dynamic interpretation of LCA results, which aims at improving the reliability of assessment of buildings’ environmental impacts. To that end, are compared: - the environmental impacts assessed for 50, 70 and then 100 years of the building’s lifetime; - and environmental impacts assessed for anytime during the first 100 years of building’s lifetime. Since the impacts depend on the type of the building’s components and their quantity, in this study two scenarios have been applied: one compares two building projects that differ from each other on the shape and functionality; the other compares two projects that differ only on components and systems employed in the building. Possible projects of the smart living building have been selected as case studies. This building aims at reaching the goals of the 2000-watt society vision and will be built by 2020 in Fribourg, Switzerland. The dynamic interpretation of building’s impacts shows that the LCA results could vary up to 20%, according to the assumed building’s lifetime and thus, completely change the conclusion in the comparison of the impacts of different building projects when the projects differ from the components and systems. The dynamic interpretation assessed more reliable LCA-results, that are useful for strengthen comparisons in the decision making process

Effect of dimensions on embodied environmental impact of buildings

Designers are faced with many options on material and technical solutions during the design phase of the building. Different studies proposing solutions and guidelines are presented in the literature. They help to guide the building project toward low CO2-eq solutions. Despite all these studies, the influence of building dimensions on embodied environmental impacts hasn’t been treated. The dimensions are the first parameters to be defined in the early design phase and can have significant influence in building’s impacts. In this study, we aim to introduce the relationship between the dimensions of the building and their influence in its embodied environmental impacts. Here we limit our study in the case of buildings with structure in cementitious materials, to derive some general principles for design. To do so first, we have assessed the environmental impacts of a single room by progressing its span. Secondly, the impacts have been assessed by multiplying the room in length, width and then in height, by transforming it into a building. Thirdly, we addressed the problem of defining optimal dimensions of a building and construction from an environmental point of view. Finally, the environmental impacts of two different structures, reinforced concrete beam-columns and shear-walls have been compared. According to the type of construction considered, earthquake forces and dimensions in plan and height the study identified the progression of the environmental impacts and the definition of optimal dimensions of the buildings. A good definition of dimensions can reduce significantly the embodied impacts of the buildings. However, further work is necessary for better identifying the optimal dimensions of building by adding to this work the impacts of operation phase